Light emitting device

ABSTRACT

A light emitting device includes a first light emitting element, a second light emitting element disposed adjacent to the first light emitting element, a first color conversion element disposed on the first light emitting element, and a second color conversion element disposed on the second light emitting element. A thickness of the first color conversion element is different from a thickness of the second color conversion element.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of the application Ser.No. 16/358,676, filed on Mar. 19, 2019. The contents thereof areincluded herein by reference.

BACKGROUND OF THE DISCLOSURE 1. Field of the Disclosure

The present disclosure relates to a light emitting device, and moreparticularly, to a light emitting device which includes a protectivelayer in a form of a multilayer structure.

2. Description of the Prior Art

The reliability of quantum dot (QD) materials is not good enough inelectronic devices. Exposure to moist or oxygen deteriorates theperformance of the quantum dots and causes the quantum dots to fail tooperate normally. The conventional QD-OLED structures cannot effectivelyprotect the quantum dots from damages because the protection layer forQD in various QD-OLED structures is very demanding.

In the QD-OLED manufacturing process, requirements for light resistance,for heat resistance, for water resistance, for oxygen resistance, andfor chemical resistance are challenging and needed. Therefore, theindustry suffers serious problems that a QD layer in various QD-OLEDstructures is not well protected by the protection structure from thedamages of light, heat, moist, oxygen and chemicals.

SUMMARY OF THE DISCLOSURE

The present disclosure provides a light emitting device which includes alight emitting device includes a first light emitting element, a secondlight emitting element disposed adjacent to the first light emittingelement, a first color conversion element disposed on the first lightemitting element, and a second color conversion element disposed on thesecond light emitting element. A thickness of the first color conversionelement is different from a thickness of the second color conversionelement.

The present disclosure will no doubt become obvious to those of ordinaryskill in the art after reading the following detailed description withrespect to various embodiments and examples which are illustrated infigures and in drawings.

These and other objectives of the present disclosure will no doubtbecome obvious to those of ordinary skill in the art after reading thefollowing detailed description of the embodiment that is illustrated inthe various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic diagram illustrating a cross-sectional view of alight emitting device according to an embodiment of the presentdisclosure.

FIG. 1B is a schematic diagram illustrating a cross-sectional view of alight emitting device according to another embodiment of the presentdisclosure.

FIG. 1C is a schematic diagram illustrating a cross-sectional view of alight emitting device according to another variant embodiment of thepresent disclosure.

FIG. 2 is a schematic diagram illustrating a top view of a pixel in alight emitting device according to another embodiment of the presentdisclosure.

FIG. 3 is a schematic diagram illustrating a cross-sectional view of aprotective layer according to other variant embodiments of the presentdisclosure.

FIG. 4 is a schematic diagram illustrating a cross-sectional view of alight emitting device according to other variant embodiments of thepresent disclosure.

FIG. 5 is a schematic diagram illustrating a cross-sectional view of aplurality of light emitting elements in a light emitting deviceaccording to another embodiment of the present disclosure.

FIG. 6 is a schematic diagram illustrating a cross-sectional view of aplurality of quantum dots in a light emitting device according toanother embodiment of the present disclosure.

FIG. 7 is a schematic diagram illustrating a cross-sectional view of alight emitting device according to another embodiment of the presentdisclosure.

FIG. 8A and FIG. 8B are schematic diagrams illustrating across-sectional view of a light emitting device according to anotherembodiment of the present disclosure.

FIG. 9 is a schematic diagram illustrating a cross-sectional view of alight emitting device according to another embodiment of the presentdisclosure.

FIG. 10A, FIG. 10B, FIG. 10C, FIG. 10D, FIG. 10E, FIG. 10F, FIG. 10G andFIG. 10H are schematic diagrams illustrating a cross-sectional view of alight emitting device according to another embodiment of the presentdisclosure.

DETAILED DESCRIPTION

The present disclosure may be understood by reference to the followingdetailed description, taken in conjunction with the drawings asdescribed below. For purposes of illustrative clarity understood,various drawings of this disclosure show a portion of the electronicdevice, and certain elements in various drawings may not be drawn toscale. In addition, the number and dimension of each device shown indrawings are only illustrative and are not intended to limit the scopeof the present disclosure.

Certain terms are used throughout the description and following claimsto refer to particular components. As one skilled in the art willunderstand, electronic equipment manufacturers may refer to a componentby different names. This document does not intend to distinguish betweencomponents that differ in name but not function. In the followingdescription and in the claims, the terms “include”, “comprise” and“have” are used in an open-ended fashion, and thus should be interpretedto mean “include, but not limited to”.

When an element or layer is referred to as being “on” or “connected to”another element or layer, it can be directly on or directly connected tothe other element or layer, or intervening elements or layers may bepresented. In contrast, when an element is referred to as being“directly on” or “directly connected to” another element or layer, thereare no intervening elements or layers presented.

The terms “about”, “substantially”, “equal”, or “same” generally meanwithin 20% of a given value or range, or mean within 10%, 5%, 3%, 2%,1%, or 0.5% of a given value or range.

Although terms such as first, second, third, etc., may be used todescribe diverse constituent elements, such constituent elements are notlimited by the terms. The terms are used only to discriminate aconstituent element from other constituent elements in thespecification. The claims may not use the same terms, but instead mayuse the terms first, second, third, etc. with respect to the order inwhich an element is claimed. Accordingly, in the following description,a first constituent element may be a second constituent element in aclaim.

The technical features in different embodiments described in thefollowing can be replaced, recombined, or mixed with one another toconstitute another embodiment without departing from the spirit of thepresent disclosure.

FIG. 1A is a schematic diagram illustrating a cross-sectional view of alight emitting device 100 according to an embodiment of the presentdisclosure. The light emitting device 100 may include a plurality oflight emitting elements 110, a pixel defining layer (PDL) 106, aplurality of spacers 115, a plurality of color conversion elements 120and a protective layer 130, but is not limited thereto. The spacers 115may optionally be disposed corresponding to the pixel defining layer(PDL) 106 such that they will not shield the light emitting regions.

In one embodiment, the light emitting elements 110 may be organiclight-emitting diodes (OLED), light-emitting diodes (LED), micro LEDs,mini LEDs or quantum dot light-emitting diodes (QLEDs), but not limitedthereto. A light emitting element 110 may emit blue light of a main peak(maximum peak) wavelength in a range of 440 nm to 470 nm for blue rayspumping, or the main peak wavelength (maximum peak) in the range of 450nm±10 nm for better optical performance.

In another embodiment, a light emitting element 110 may emit mixed rays.For example, the mixed rays are formed by mixing blue light having themain peak wavelength (maximum peak) in the range from 461 nm to 473 nmand another blue light having the main peak wavelength (maximum peak) inthe range from 440 nm to 460 nm wherein the light emitting element 110may include two light emitting components (such as light emittinglayers) in a stack structure, one of them can emit the blue light havingthe main peak (maximum peak) wavelength at about 450 nm, and another onecan emit the blue light having the main peak (maximum peak) wavelengthat about 467 nm. These light emitting components may be stackedvertically or disposed horizontally (e.g. side by side) within oneelectronic unit. In some embodiments, the light emitting element 110 mayinclude one or more light emitting components.

Alight emitting element 110 may include a first electrode layer 111, asecond electrode layer 112, and a light emitting layer 113. When thelight emitting element 110 is an OLED, the light emitting layer 113 mayinclude, but not limited to, a hole injection layer (HIL), a holetransport layer (HTL), an emissive layer (EL), an electron transportlayer (ETL), an electron injection layer (EIL) and/or a chargegenerating layer (CGL) for example. The emissive layer may include asuitable organic light emitting material and is useful for pumpingsuitable blue light. Further, the first electrode layer 111 may be oneof a cathode and an anode, and the second electrode layer 112 may be acorresponding anode or cathode, depending on the type of the firstelectrode layer 111. The light emitting layer 113 may contact or may notcontact the adjacent spacer 115.

The second electrode layer 112 may be disposed on a passivation layer140, a connection element 112′ may penetrate through the passivationlayer 140 to electrically connect the second electrode layer 112 to atransistor 141 of the light emitting device 100. In one embodiment, thesecond electrode layer 112 may be formed along with the connectionelement 112′ at the same time to be one integrally formed element. Inanother embodiment, the second electrode layer 112 may be formed afterthe formation of the connection element 112′.

For example, the transistor 141 may be a thin film transistor (TFT) incharge of the on/off state of the above light emitting element 110. Thefirst electrode layer 111 and the second electrode layer 112 which iselectrically connected to a transistor 141 to control the on/off stateof the corresponding light emitting element 110. In other embodiments,the above layers may be optionally added or removed depending on thesituation, and they are not limited thereto. The first electrode layer111 may be a common electrode for a plurality of light emitting elements110.

TFTs 141 may serve as switch elements for driving the light emittingelements 110 in the light emitting device 100. The TFTs 141 may includea semiconductor layer 142, a drain electrode 143, a source electrode144, and a gate electrode 145. The semiconductor layer comprises asemiconductor material, such as silicon or metal oxide, but not limitedthereto. For example, the semiconductor layer may comprise amorphoussilicon, polysilicon, or indium gallium zinc oxide (IGZO). Thesemiconductor layer may include a source contact, a drain contact, and achannel disposed between the source contact and the drain contact in oneTFT 141. The drain electrode and the source electrode are electricallyconnected to the semiconductor layer respectively. The gate electrode isseparated from the channel by a gate dielectric layer. The gateelectrode, the source electrode and the drain electrode may compriseconductive materials (such as metal, but not limited thereto). It shouldbe noted that the structure of the TFTs 141 shown in FIG. 1 is merely anexample and is not meant to limit the possible types or structures ofthe TFTs 141 of the present disclosure, and any other suitable TFTstructures may replace the illustrated TFTs 141. For example, top-gatetype TFTs or bottom-gate type TFTs may be used as the TFTs 141 in avariant embodiment.

FIG. 1B is a schematic diagram illustrating a cross-sectional view of alight emitting device according to a variant first embodiment of thepresent disclosure. In FIG. 1B, a plurality of light emitting elements110 may include a plurality of micro LEDs or mini LEDs 114, a cathode111′ and an anode layer 112 in the absence of a spacer. In other words,the second electrode layer may be the anode layer 112. The micro LEDs ormini LEDs 114 are in the form of a vertical type and may share a commoncathode layer, i.e. the first electrode layer 111 for example, atop themicro LEDs or mini LEDs 114.

FIG. 1C is a schematic diagram illustrating a cross-sectional view of alight emitting device according to another variant first embodiment ofthe present disclosure. In FIG. 1C, a plurality of light emittingelements 110 may include a plurality of micro LEDs or mini LEDs 114, acathode 111′ and an anode layer in the absence of a spacer. For example,the second electrode layer 112 may be the anode layer. The micro LEDs ormini LEDs 114 are in the form of a flip-type and may share a commoncathode layer, i.e. the first electrode layer 111 for example, atop themicro LEDs or mini LEDs 114. Both the cathode 111′ and the anode layerare disposed under the pixel defining layer (PDL) 106 and accordinglyco-planar. The micro LEDs or mini LEDs 114 may be disposed within aninsulating layer 146.

The color conversion elements 120 may be wavelength conversion elementsto adjust the output light of the light emitting device 100. Forexample, the color conversion elements 120 may include quantum dots,phosphor material, a dye or a color filter. The quantum dots may be madeof a semiconductor nano-crystal structure, and can include CdSe, CdS,CdTe, ZnSe, ZnTe, ZnS, HgTe, InAs, Cd_(1-x)Zn_(x)Se_(1-y)S_(y),CdSe/ZnS, InP, and GaAs, but not limited thereto. Quantum dots generallyhave a particle size between 1 nm and 30 nm, 1 nm and 20 nm, or 1 nm and10 nm. When quantum dots 121, 122 are excited by input light, the inputlight will be converted into an emitted light with other colors byquantum dots. The colors of the emitted light may be adjusted by thematerial or size of the quantum dots. In some embodiments, the quantumdots may include sphere particles, rod particles or particles with anyother suitable shapes as long as the quantum dots could emit light withsuitable color. The color conversion elements 120 may be useful foroutputting visible light. For example, the color conversion element 120may output blue light, cyan light, green light, yellow light, red lightor a combination thereof. In the present disclosure, the above outputlight could be regarded as the final visual light of the light emittingdevice 100 perceived by the user (observer).

The plurality of color conversion elements 120 may be disposed on atleast a portion of the plurality of light emitting elements 110 anddefined by a pixel defining layer (PDL) 106. In one embodiment, theplurality of color conversion elements 120 are disposed on the pluralityof light emitting elements 110 respectively. For example, a colorconversion element 120 is disposed on a light emitting element 110, butnot limited thereto. In another embodiment, the plurality of colorconversion elements 120 are disposed on only a portion of the pluralityof light emitting elements 110. Or in still another embodiment, notevery light emitting element 110 has a color conversion element 120disposed thereon, but not limited thereto.

The protective layer 130 is disposed on the plurality of colorconversion elements 120 to keep the light emitting elements 110, or thecolor conversion elements 120 from damages, such as the damages whichare caused by moist or oxygen. The protective layer 130 is in a form ofa multilayer structure, such as a stack structure including multiplelayers. In one embodiment, the protective layer 130 has a top surface139. For example, the protective layer 130 may include at least oneinorganic layer 131 of a thickness Ti1 and at least one organic layer132 of a thickness To. The inorganic layer 131 may be a functionalinorganic layer and the organic layer 132 may be a functional organiclayer.

In another embodiment, at least one inorganic layer 133 of a thicknessTi2 in the protective layer 130 may conformally cover the light emittingelements 110 so that such inorganic layer 133 in the protective layer130 may not flat. In still another embodiment, if one inorganic layer131 is atop an organic layer 132 with a top surface 132 t, suchinorganic layer 131 may accordingly have a surface 131 t as well. Oneorganic layer 132 may stack on one inorganic layer 133 or one inorganiclayer 131 may be disposed on one organic layer 132. There may be anotherinorganic layer 129 disposed between the protective layer 130 and thecolor conversion elements 120. Each thickness Ti1, To or Ti2 may bedetermined above or under the color conversion element 120.

The organic layer 132 may comprise an organic material and provide asurface for the inorganic layer 131 atop the organic layer 132 to makethe inorganic layer 131 have a surface as well. For example, the organiclayer 132 may be a color filter layer of a thickness of 2 μm to 3 μm tofacilitate the improvement of the optical performance of the lightemitting device 100, but not limited thereto. Or alternatively, theorganic layer 132 may comprise a transparent polymeric material. Forexample, the polymeric material may comprise an acrylic material or ameth-acrylic material.

FIG. 2 is a schematic diagram illustrating a top view of a pixel 101 ina light emitting device 100 according to another embodiment of thepresent disclosure. Generally speaking, the organic layer 132 may standastride at least two sub-pixels, for example a red sub-pixel 102, agreen sub-pixel 103, or further stand astride a blue sub-pixel 104, orstand astride three or more sub-pixels so a pixel 101 may have three ormore sub-pixels of different colors. The protective layer 130 istransparent with respect to a specific wavelength of light, for exampleblue light, cyan light, green light, yellow light or red light.

FIG. 3 is a schematic diagram illustrating a cross-sectional view of aprotective layer 130 according to variant embodiments of the presentdisclosure. In a variant embodiment A1 of the present disclosure, theprotective layer 130(I) may consist of one organic layer 132 and oneinorganic layer 131 atop the organic layer 132. This configuration hasthe simplest structure which meets the requirement of the protectivelayer 130 of the present disclosure. In another variant embodiment A2,the protective layer 130(11) may consist of one organic layer 132 whichis sandwiched between a first inorganic layer 131 and a second inorganiclayer 133. The top inorganic layer 131 in this configuration may serveas a shield of the organic layer 132 to make it harmlessly pass processsteps in a later stage. The organic layer 132 in this configuration mayprovide the inorganic layer 131 with a bottom and a robust support. Thebottom inorganic layer 133 in this configuration may serve as a bufferlayer between the organic layer 132 and the color conversion element120.

In another variant embodiment A3, the protective layer 130(111) mayinclude three inorganic layers 131, 133, 135. In another variantembodiment A4, the protective layer 130 (IV) may include at least twoorganic layers 132, 134 and at least two inorganic layers 131, 133. Inanother variant embodiment A5, the protective layer 130(V) may include afunctional organic layer 134 f to be the topmost layer. For example, thefunctional organic layer 134 f may be a color filter layer. In anothervariant embodiment A5′, the protective layer 130(V′) may include afunctional inorganic layer 131 f to be the topmost layer. For example,the functional inorganic layer 131 f may be a distributed Braggreflector (DBR) layer. In other variant embodiments, the protectivelayer (VI) may include six to nine layers with alternating inorganiclayers I and organic layers O.

In the variant embodiments of the protective layer 130, the thickness ofthe organic layer 132 may be greater than that of the inorganic layer131. Or, the thickness of the first inorganic layer 131 may be equal toor different from that of the second inorganic layer 133. In oneexample, a thinner inorganic layer is easier to form, and in anotherexample a thicker inorganic layer facilitates better protection of thelight emitting device 100. Generally speaking, a transmittance of theprotective layer 130 with respect to red light may be 50% or higher forbetter optical performance. A transmittance of the protective layer 130with respect to green light may be 30% or higher for better opticalperformance. A transmittance of the protective layer 130 with respect toblue light may be 24% or higher for better optical performance.

An inorganic layer may comprise an insulating material or a conductivematerial. An insulating material, for example a distributed Braggreflector (DBR) layer of a thickness of 1000 Å to 1μ, may facilitate theimprovement of the optical performance of the light emitting device 100.The protective layer 130 may include one or more insulating inorganiclayers.

Referring back to FIG. 1, a conductive material may serve as anauxiliary electrode to facilitate the improvement of IR drop of theelectrode layers 111, 112 atop the light emitting elements 110 of thelight emitting device 100 in case an insufficient driving voltage owingto long distance causes the IR drop. A conductive material may comprisea metal layer such as a thin silver film of a thickness of 50 Å to 200Å, an alloy layer such as a thin magnesium-indium film, or a transparentconductive material such as indium tin oxide (ITO) or indium galliumzinc oxide (IGZO). The conductive inorganic layer may be any inorganiclayer in the protective layer.

FIG. 4 is a schematic diagram illustrating a cross-sectional view of alight emitting device 100 according to variant embodiments of thepresent disclosure. In one variant embodiment B1, the protective layer130 may include a distributed Bragg reflector (DBR) layer 131 f and anorganic color filter 132 f. This simple configuration in one aspect hasboth the benefits of DBR layer and the color filter to improve theoptical performance of the light emitting device 100 and in anotheraspect helps simplify the process to manufacture the light emittingdevice 100. There may be the inorganic layer 129 disposed between theprotective layer 130 and the light emitting elements 110.

In another variant embodiment B2, the protective layer 130 may include aDBR layer 131 f, an inorganic electric conductive layer 133 f and anorganic color filter 132 f which is sandwiched between the DBR layer 131f and the inorganic electric conductive layer 133 f. This simpleconfiguration in one aspect has the benefits of the DBR layer and thecolor filter to improve the optical performance of the light emittingdevice 100, the benefit of the conductive layer to improve the problemof IR drop of the electrode layers 111, 112 of the light emitting device100, and in another aspect helps simplify the process to manufacture thelight emitting device 100. In still another variant embodiment B3, theprotective layer 130 may include a couple of DBR layers 131 f, 133 f toform a gain resonator. This configuration helps form laser-like outputlight and facilitates better optical performance of the light emittingdevice 100.

The topmost layer of the protective layer 130 may comprise either anorganic material or an inorganic layer. The bottommost layer of theprotective layer may comprise either an organic material or an inorganiclayer. A protective layer 130 may include a couple of DBR layers for theconcentration of the wavelength of the output of the light of the lightemitting device 110.

Referring to FIG. 5 and FIG. 1, FIG. 5 is a schematic diagramillustrating a cross-sectional view of a plurality of light emittingelements 110 in a light emitting device 100 according to anotherembodiment of the present disclosure. In one embodiment, a plurality ofcolor conversion elements 120 are disposed on a bulk layer 113′ whichserve as a light emitting layer. This configuration helps simplify theprocess to manufacture the light emitting device 100 by omitting a maskto define the pattern of the light emitting elements 110. In anothervariant embodiment, a plurality of color conversion elements 120 aredisposed on a corresponding light emitting layer 113, namely aside-by-side structure and the formation of the spacers 115 is prior tothe formation of the light emitting layers 113, so the light emittinglayer 113 is continuous atop of the spacers 115 and the color conversionelements 120 are segregated by the pixel defining layer (PDL) 106. Instill another embodiment, the spacers 115 may be optionally disposedatop of the first electrode 111, of the light emitting layer 113 and ofthe protective layer 130. The formation of spacers 115 may avoid theoverflow of a quantum dot material before curing.

Referring to FIG. 6 and FIG. 1, FIG. 6 is a schematic diagramillustrating a cross-sectional view of a plurality of quantum dots 121,122, 123 in a light emitting device 100 according to another embodimentof the present disclosure. In the embodiment of FIG. 1, the bluesub-pixel 104 is free of a color conversion element. This configurationhelps simplify the process to manufacture the light emitting device byomitting a step to form the color conversion element 120 in the bluesub-pixel 104. In the variant embodiment of FIG. 6, there is a colorconversion element 123 disposed in the blue sub-pixel 104. Thisconfiguration may help adjust the blue ray composition of the outputlight or adjust the shift of the wavelength of the blue sub-pixel 104.

Please refer to FIG. 5 and FIG. 7. FIG. 7 is a schematic diagramillustrating a cross-sectional view of a light emitting device 100according to another embodiment of the present disclosure. In onevariant embodiment of FIG. 5, the light emitting device 100 may have aplurality of cavities 116, 117 to accommodate each different colorconversion element 120, such as quantum dots 121, 122 so the colorconversion elements 120 are respectively and individually disposed inthe cavities 116, 117.

Optionally, each quantum dot 121, 122 may sufficiently fill one cavity,or alternatively in another variant embodiment of FIG. 7, the quantumdots 121, 122 may fill up the cavities 116, 117. If the quantum dots121, 122 fill up the cavities 116, 117, the spacers 115 nearby help toavoid the problem of the overflow of the quantum dot material beforecuring. As shown in the figures, the thickness of the organic layer 132is usually higher than the height of a spacer 115. FIG. 5 illustrates anover-coating blue OLED structure of a continuous light emitting layer.FIG. 7 illustrates a side-by side structure of a discontinuous lightemitting layer.

Please refer back to FIG. 1. The organic layer 132 may generally have athickness To greater than a thickness Tg of the color conversion element120. For example, if the color conversion elements 120 are disposed inthe cavities 116, 117, the organic layer 132 may generally have athickness To in a range from 2 μm to 50 μm, and the color conversionelements 120, such as the quantum dots 121, 122, may generally have athickness Tg in a range from 1 μm to 10 μm (measured from the topsurface to the bottom surface of the color conversion element 120accommodated in a cavity 116 or 117). Further, a ratio (Tg/To) of thethickness Tg of a color conversion element 120 to the thickness To of anorganic layer 132 may range from 10% to 150%.

Refer to FIG. 1, FIG. 8A and FIG. 8B, FIG. 8A or FIG. 8B is a schematicdiagram illustrating a cross-sectional view of a light emitting device100 according to another embodiment of the present disclosure. In onevariant embodiment of FIG. 1, the protective layer 130 has a top surface131 t, and the top surface 131 t may be substantially flat and has norecess to vertically correspond to the sub-pixels 102, 103, 104. Thethickness of the protective layer 130 is determined vertically from thetop surface 131 t of the inorganic layer 131 to the interface of thecolor conversion element 120 and the inorganic layer 133 in thesub-pixels 102, 103. This configuration helps simplify the process tomanufacture the light emitting device 100.

In another variant embodiment of FIG. 8A, the top surface 131 t includesa recess 109 to correspond to and overlap a blue sub-pixel 104. Therecess 109 helps decrease the regional thickness Tp of the protectivelayer 130 to increase the intensity of the light so a quantum dot in onesub-pixel may not be needed. If a color conversion element is absentfrom a cavity 118, the thickness Tp of the protective layer 130 isdetermined vertically from the bottom of the recess 118 to the topsurface 131 t in a blue sub-pixel 104. In an embodiment, differentsub-pixels may accordingly have different ratios (Tg/Tp) with or withoutthe recess.

In another variant embodiment of FIG. 8B, the top surface 131 t includesa plurality of recesses 107, 108, 109 to correspond to and overlapdifferent sub-pixels such as a red sub-pixel 102, a green sub-pixel 103or a blue sub-pixel 104 respectively. The recesses 107, 108, 109 helpdecrease the regional thickness Tp1 of the protective layer 130 toincrease the intensity of the light so double light emitting elements inone sub-pixel may not be needed. If a color conversion element 120 ispresent in a cavity 117, the thickness Tp2 of the protective layer 130is determined vertically from the inorganic layer 129 to the top surface131 t in a red sub-pixel 102 or a green sub-pixel 103. When Tp1>Tp2, theintensity of the blue light of the blue sub-pixel 104 would be strongerbecause the blue light of the blue sub-pixel 104 does not pass quantumdots. When Tp2>Tp1, the output light of the blue sub-pixel 104 is lessbluish because a thicker Tp2 consumes more blue light.

FIG. 9 is a schematic diagram illustrating a cross-sectional view of alight emitting device 100 according to another embodiment of the presentdisclosure. In one embodiment, the color conversion elements 120 aredisposed on a surface 151 of a planarization layer 150. Theplanarization layer 150 fills up the cavities 116, 117 and has a topsurface 151. Each color conversion element 120, such as quantum dots121, 122, is in direct contact with the top surface 151 and completelycovered by the organic layer 132. Because the quantum dots 121, 122, arenot disposed in the cavities 116, 117, variable depth of the cavities116, 117 to jeopardize the optical performance of the light emittingdevice 110 may be accordingly avoided. In FIG. 9, a quantum dot 121 or122 is not accommodated in a cavity 116, 117 and the planarization layer150 fills the cavities 116, 117. The suitable material for theplanarization layer 150 may comprise an inorganic material, such assilicon oxide, silicon nitride, silicon oxynitride, metal oxide, or anorganic material, such as polyimide, acrylate, epoxy, poly(methylmethacrylate), benzocyclobutene or polyester).

Please refer to FIG. 10A, FIG. 10B, FIG. 10C, FIG. 10D, FIG. 10E, FIG.10F, FIG. 10G and FIG. 10H. FIG. 10A, FIG. 10B, FIG. 10C, FIG. 10D, FIG.10E, FIG. 10F, FIG. 10G or FIG. 10H is a schematic diagram illustratinga cross-sectional view of a light emitting device 100 according toanother embodiment of the present disclosure. The optional blackmatrixes 160 are present in the light emitting device 100 of theembodiments. The optional black matrixes 160 may be disposed between twoadjacent sub-pixels and may help avoid the cross-talk of light from theneighboring sub-pixels.

For example, in a variant embodiment C1 of FIG. 10A, the black matrixes160 are disposed in the organic layer 132 and above the color conversionelements 120. The black matrixes 160 are in a shape of a trapezoid. Orin a variant embodiment C2 of FIG. 10B, both the black matrixes 160 andthe color conversion elements 120 are disposed in the organic layer 132and above a planarization layer 150 so the black matrixes 160 are indirect contact with the color conversion elements 120, with theplanarization layer 150 and with the organic layer 132. In FIG. 10B, thequantum dot 121 or 122 is not accommodated in a cavity 116 or 117 andthe planarization layer 160 fills up the cavities 116, 117. Further, theblack matrixes 160 are disposed between two adjacent quantum dots.

Or in a variant embodiment C3 of FIG. 10C, if the color filters 134 fserve as the organic layer, the black matrixes 160 are sandwichedbetween two adjacent color filters 134 f. Each black matrix 160 isdisposed atop a corresponding spacer 115 and a color filter 134 f isdisposed atop a corresponding light emitting element 110 and in directcontact with the color conversion elements 120. The black matrixes 160are in a shape of a trapezoid. Moreover, the color filters 134 f and theblack matrixes 160 together are arranged in a lateral direction witheach other. This configuration helps simplify the process to manufacturethe light emitting device. Or in a variant embodiment C4 of FIG. 10D,the DBR layer 131 f may serve as a topmost layer. The introduction ofthe DBR layer 131 f may help improve the optical performance of thelight emitting device 100.

Or in a variant embodiment C5 of FIG. 10E, if the color filters 134 fserve as the organic layer and the color conversion elements 120 aredisposed on the planarization layer 150, the black matrixes 160 aresandwiched between two adjacent color filters 134 f, or between twoadjacent quantum dots 121 and 122. Each black matrix 160 is disposedatop the planarization layer 150 and each color filter 134 f is disposedatop the planarization layer 150, too. The black matrixes 160 are in ashape of a trapezoid. This configuration helps provide a better lightpath.

Or in a variant embodiment C6 of FIG. 10F, if both the color filters 134f and the organic layer 132 are present and the color conversionelements 120 are disposed under the organic layer 132, both the colorfilters 134 f and the black matrixes 160 are disposed atop the organiclayer 132. The black matrixes 160 are sandwiched between two adjacentcolor filters 134 f and in a shape of an inverted trapezoid. Both thecolor filters 134 f and the organic layer 132 provide protection so thisconfiguration facilitates a robust protective layer. Or in a variantembodiment C7 of FIG. 10G, the variant embodiment C6 may further includea DBR layer 131 f to serve as a topmost layer. The introduction of theDBR layer 131 f helps improve the optical performance of the lightemitting device 100.

Or in a variant embodiment C8 of FIG. 10H, if both the color filters 134f and the organic layer 132 are present and the color conversionelements 120 are disposed on the planarization layer 150, both the colorfilters 134 f and the black matrixes 160 are disposed atop the organiclayer 132, and both the organic layer 132 and the color conversionelements 120 are disposed atop the planarization layer 150. The blackmatrixes 160 are in a shape of an inverted trapezoid. This configurationalso facilitates a robust protective layer.

Please refer back to FIG. 3. The light emitting device 100 may furthercomprise a blue light blocking layer disposed on the topmost inorganiclayer I, as shown in the variant embodiment A5 or in the variantembodiment A5′. Because the conversion efficiency of a color conversionelement 120 is not 100%, a portion of the light which is emitted fromthe light emitting element 120 may not be completely converted by theabove color conversion element 120, so the spectrum of the output lightof a sub-pixel may include a target wave and a sub-wave. The target wavemay represent the converted light and the sub-wave may represent theunconverted light. The sub-wave in the output light jeopardizes theoptical performance of the light emitting device 100.

In the present disclosure, an optional blue light blocking layer mayhelp to block the leaking sub-wave in the output light. The blue lightblocking layer may be a color filter layer 134 f or a DBR layer 131 f.In another variant embodiment, the blue light blocking layer may be thetopmost layer of the protective layer 130.

TABLE 1 demonstrates that various structural types may be optionallycombined to results in variant embodiments. Type I Type II Type IIILight emitting layer bulk layer side-by-side black matrix present absentblue light blocking layer color filter DBR colorless organic layerpresent absent planarization layer present absent recess present absent

In summary, the present disclosure provides a QD layer in variousQD-OLED structures with a protective multilayer structure. This novelprotection structure renders the fragile quantum dots in a QD-OLED lightemitting device well protected to have robust resistance to light, toheat, to moist, to oxygen and to chemicals so as to overcome the currentproblems in the industry.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the disclosure. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A light emitting device, comprising: a firstlight emitting element; a second light emitting element disposedadjacent to the first light emitting element; a first color conversionelement disposed on the first light emitting element; and a second colorconversion element disposed on the second light emitting element;wherein a thickness of the first color conversion element is differentfrom a thickness of the second color conversion element.
 2. The lightemitting device of claim 1, wherein the first light emitting elementcomprises a portion of a light emitting layer, the second light emittingelement comprises another portion of the light emitting layer, and thelight emitting layer is a continuous layer across the first lightemitting element and the second light emitting element.
 3. The lightemitting device of claim 2, further comprising a pixel defining layer,wherein the light emitting layer is in contact with a top surface of thepixel defining layer.
 4. The light emitting device of claim 3, whereinthe first light emitting element comprises a first electrode and asecond electrode, wherein the portion of the light emitting layer isdisposed between the first electrode and the second electrode, and thefirst electrode and the second electrode overlap with the pixel defininglayer.
 5. The light emitting device of claim 1, wherein a surface of atleast one of the first color conversion element is curved.
 6. The lightemitting device of claim 1, further comprising: an insulating layerdisposed between the first light emitting element and the first colorconversion element.
 7. The light emitting device of claim 1, furthercomprising: a first transistor electrically connected to the first lightemitting element, wherein the first color conversion element overlapswith the first transistor.
 8. The light emitting device of claim 7,wherein the first transistor comprises a semiconductor layer, and thefirst color conversion element overlaps with the semiconductor layer. 9.The light emitting device of claim 8, wherein the semiconductor layercomprises amorphous silicon, polysilicon, or indium gallium zinc oxide(IGZO).
 10. The light emitting device of claim 1, wherein at least oneof the first color conversion element or the second color conversionelement comprises a color filter.